In `TangentBuilder` temporary allocations are emitted in order to make generic calls to `AdditiveArithmetic.zero` and `AdditiveArithmetic.+`. When we perform accumulation of two adjoint values that correspond to a lexical value in the original function, the stack allocations require a debug variable, as we use the original instruction's location. However such a debug variable wouldn't really make sense as these temporary allocations do not represent the original variable's adjoint. With lexical borrow scopes, we hit a crasher when creating temporary allocations when accumulating adjoints for lexical `begin_borrow` instructions.
This PR makes `TangentBuilder`'s temporary allocations use an auto-generated location. The existing debug info emission behavior is not changed, as we still emit `debug_value` when materializing an `AdjointValue` after any necessary adjoint accumulation.
Refactor SILGen's ApplyOptions into an OptionSet, add a
DoesNotAwait flag to go with DoesNotThrow, and sink it
all down into SILInstruction.h.
Then, replace the isNonThrowing() flag in ApplyInst and
BeginApplyInst with getApplyOptions(), and plumb it
through to TryApplyInst as well.
Set the flag when SILGen emits a sync call to a reasync
function.
When set, this disables the SIL verifier check against
calling async functions from sync functions.
Finally, this allows us to add end-to-end tests for
rdar://problem/71098795.
- Properly clone and use debug scopes for all instructions in pullback functions.
- Emit `debug_value` instructions for adjoint values.
- Add debug locations and variable info to adjoint buffer allocations.
- Add `TangentBuilder` (a `SILBuilder` subclass) to unify and simplify special emitter utilities for tangent vector code generation. More simplifications to come.
Pullback variable inspection example:
```console
(lldb) n
Process 50984 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
frame #0: 0x0000000100003497 main`pullback of foo(x=0) at main.swift:12:11
9 import _Differentiation
10
11 func foo(_ x: Float) -> Float {
-> 12 let y = sin(x)
13 let z = cos(y)
14 let k = tanh(z) + cos(y)
15 return k
Target 0: (main) stopped.
(lldb) fr v
(Float) x = 0
(Float) k = 1
(Float) z = 0.495846391
(Float) y = -0.689988375
```
Resolves rdar://68616528 / SR-13535.
